Novel valve employing hydrophobic and hydrophilic membranes

ABSTRACT

A novel valve employing hydrophobic and hydrophilic membranes and providing a combined air barrier and liquid sequencing valve. The novel valve is useful in gravitational flow systems and equipment sets for the sequential administration of medical liquids, wherein a primary liquid can be administered at a flow rate independent of the flow rate of a secondary liquid, and includes barriers substantially impervious to air to prevent the inadvertent administration of air when the liquids are depleted.

BACKGROUND OF THE INVENTION

The present invention relates to systems and equipment sets for theadministration of medical liquids to a patient, and more particularly,to systems and equipment sets for the sequential administration of aplurality of medical liquids employing a novel hydrophobic andhydrophilic membrane valve providing a combined air barrier and liquidsequencing valve therefor.

The parenteral administration of medical liquids to patients is a longestablished practice. Liquids including amino acids, blood, dextrose,electrolytes, and saline are commonly administered to patients overprolonged periods of time. Generally, these liquids are administeredfrom a glass bottle or plastic bag suspended above the patient andcontaining 250-2,000 ml. of the liquid. Such prolonged infusionscommonly are administered at a flow rate of 10-150 ml./hr.

Frequently, the patient must receive an additive or secondary liquidwhile the prolonged infusion is being administered. Preferably, thissecondary liquid should be administered through the same hypodermicneedle to avoid unnecessary pain and trauma to the patient of additionalvenipunctures. To avoid dilution and incompatability problems, it isalso preferable that the flow of the primary liquid employed in theprolonged infusion be temporarily interrupted, the secondary liquidadministered and the flow of the primary liquid resumed. Generally, thesecondary liquid will be administered at a flow rate of 50-250 ml./hr.

Abbott Laboratories, North Chicago, Ill. manufactures a y-type set forthe sequential administration of primary and secondary liquids. TheseVENOSET piggyback sets allow the prolonged infusion of a primary liquidto be temporarily halted by means of a backcheck valve in the primaryliquid flow path to administer a secondary liquid without the need for anew venipuncture. Then, when the secondary liquid has been depleted, thebackcheck valve automatically opens to resume flow of the primaryliquid. An important characteristic of this system is that the secondaryliquid container must be suspended at a higher height than the primaryliquid container to establish the liquid pressure differential thatcloses the backcheck valve in the primary liquid flow path.

A similar system is disclosed in U.S. Pat. No. 3,886,937 granted June 3,1975 to D. Bobo, et al., assigned to American Hospital Supply Corp., andentitled "Medical Administration Set for Dispensing Plural MedicalLiquids". Another similar system is disclosed in U.S. Pat. No. 4,105,029granted Aug. 8, 1978 to R. Virag, assigned to Baxter Travenol andentitled "Intravenous Solution Set Having An Air Access Site andConstricted Inner Diameter Portion".

An inherent disadvantage of the above-mentioned prior art medical liquidadministration systems is that they each resume the flow of primaryliquid at the rate the secondary liquid had been flowing. Because thepreferred flow rate of the secondary liquid is generally greater thanthe preferred flow rate of the primary liquid, when the primary liquidresumes flow at that rate, the patient can be administered an excessiveamount of primary liquid, unless the flow rate of the primary liquid isadjusted to the preferred primary liquid flow rate soon after the flowof primary liquid resumes.

A remedy to the above-described disadvantage would appear to be providedby simply incorporating flow control devices into both the primary andsecondary liquid flow paths. However, while this remedy does providedual flow rates for the primary and secondary liquids, it isunacceptable. That is, because the common tube of the y-set must be ableto accommodate both flow rates, when the primary liquid is flowing at aslower rate than the secondary liquid was, there will be an unfilledvolume or void in the common tube. To fill that void, air will be drawninto the common tube from the depleted secondary container. That airwill then be driven into the patient by the weight of the primaryliquid, thereby causing a serious embolism and perhaps, the patient'sdeath.

Accordingly, it will be apparent that a device for sequencing the flowof a plurality of liquids and preventing the flow of air therethroughwhen the liquids have been depleted would be advantageous to the medicalprofession.

SUMMARY OF THE INVENTION

The primary object of the present invention, therefore, is to provide acombined air barrier and liquid sequencing valve for the sequentialadministration of medical liquids at dual flow rates that will not drawair from the liquid containers when the liquids have been depleted.

In accordance with this and other objects, there is provided by thepresent invention a gravitational flow system for the sequentialadministration of medical liquids to a patient including a primaryliquid container, a primary tube, a secondary liquid container, asecondary tube, and a common tube all connected in fluid communicationto form a primary liquid flow path and a secondary liquid flow path. Theprimary liquid flow path includes the primary and common tube, while thesecondary liquid flow path includes the secondary and common tubes.

To establish the dual flow rates of the primary and secondary liquids, asecondary flow control means in the secondary liquid flow path foradjusting the flow rate of the secondary liquid and a primary flowcontrol means on the primary tube for adjusting the flow rate of theprimary liquid to a rate independent of the flow rate of the secondaryliquid are provided.

The primary tube includes a valve which allows primary liquid to flowfrom the primary container whenever the height of primary liquid isgreater than or equal to the height of the secondary liquid in thesystem. The valve prevents primary liquid from flowing out of theprimary container whenever the height of the primary liquid is less thanthe height of the secondary liquid in the system. The valve is alsoimpermeable by air when the primary liquid is depleted from the primarycontainer. An air barrier in the secondary liquid flow path that issubstantially impervious to air is provided to insure that no air isdrawn from the secondary container when the secondary liquid isdepleted. The secondary tube air barrier and primary tube valve arehoused in a combined air barrier and liquid sequencing valve.

BRIEF DESCRIPTION OF THE DRAWING

Other objects and attendant advantages will become obvious to thoseskilled in the art by reading the following detailed description inconnection with the accompanying drawing, wherein like referencecharacters designate like or corresponding parts throughout the severalfigures thereof and wherein:

FIG. 1 is a schematic block diagram of the efficacious system for thesequential administration of medical liquids at dual flow ratescontemplated by this invention, and

FIGS. 2-5 are front elevational views partially in cross-sectionillustrating the operation of a medical liquid administration equipmentset embodying the system of FIG. 1 and employing the novel combined airbarrier and liquid sequencing valve of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawing, there is shown in FIG. 1, a schematic blockdiagram of the basic elements of the gravitational flow system for thesequential administration of medical liquids at dual flow ratescontemplated by this invention.

The diagram depicts a primary liquid container 11 that contains aprimary medical liquid to be administered to a patient for a prolongedperiod of time. The diagram also depicts a secondary liquid container 13that contains a secondary medical liquid to be administered to thepatient for a relatively short period of time, during which time theadministration of the primary liquid will be temporarily interrupted. Asshown in the sets of FIGS. 2 and 5, containers 11 and 13 can be glassbottles, plastic flexible bags, or any other suitable container.

Primary container 11 and secondary container 13 are connected in fluidcommunication to a conventional hypodermic needle 15 through a primarytube 17, a secondary tube 19, and a common tube 21. Thus, the primaryliquid flow path from primary container 11 to needle 15 comprisesprimary tube 17 and common tube 21. Likewise, the secondary liquid flowpath from secondary container 13 to needle 15 comprises secondary tube19 and common tube 21.

The distal end of primary tube 17 is in fluid communication with primarycontainer 11, preferably by means of a piercing pin 23 inserted into apuncturable closure of container 11. Piercing pin 23 can have anintegral drip chamber 25, and when container 11 is a glass bottle, asshown in the set of FIG. 2, an integral, filtered air vent 27. Suchpiercing pins, drip chambers and air vents are well known in the medicalpractice and need not be more fully explained here.

The proximal end of primary tube 17 is joined in fluid communication tothe distal end of common tube 21, preferably by a y-tube 29, it beingunderstood that the primary, secondary and common legs of y-tube 29constitute a portion of the primary, secondary and common tubes 17, 19and 21, respectively. Primary tube 17 has a primary flow control 31 atany convenient location intermediate its ends for independentlyadjusting the rate of flow of the primary liquid through the primaryliquid flow path. Preferably, as shown in FIGS. 2-5, primary flowcontrol 31 can be a roller clamp. However, it can be any otheradjustable device that will reliably maintain a desired primary liquidflow rate.

The distal end of secondary tube 19 is in fluid communication withsecondary container 13, preferably, by means of a piercing pin 35inserted into a puncturable closure of container 13. Piercing pin 35 canhave an integral drip chamber 37, and when container 13 is a glassbottle, as shown in FIG. 2, an integral, filtered air vent 39. Theproximal end of secondary tube 19 is joined in fluid communication tothe distal end of common tube 21, preferably, by a y-tube 29.

A secondary flow control 43 is disposed at any convenient location inthe secondary liquid flow path. Preferably, as shown in FIGS. 2-5,secondary flow control 43 can be a roller clamp. However, it can be anyother adjustable device that can reliably maintain a desired secondaryfluid flow rate.

A combined air barrier and liquid sequencing valve having a housing 32is shown in FIG. 1. Housing 32 has first and second chambers 33, 41, asshown in FIGS. 2-5, that are formed by a vertical wall 34. First andsecond chambers 33, 41 each have inlet and outlet ports thereto throughhousing 32 that are respectively connected in fluid communication to theother portions of the primary or secondary tubes 17, 19. Primary tube 17thus includes first chamber 33 of housing 32, while secondary tube 19includes second chamber 41.

First chamber 33 has valve means associated with its ports that allowprimary liquid to flow from primary container 11 whenever the height ofthe primary liquid is greater than or equal to the height of thesecondary liquid in the system of FIG. 1. Further, the valve meansassociated with first chamber 33 prevents the flow of primary liquidfrom primary container 11 whenever the height of the primary liquid isless than the height of the secondary liquid in the system.

As shown in FIG. 2 and more fully explained in the following explanationof the operation of the sets of this invention, the valve meansassociated with first chamber 33 is a hydrophilic membrane 38 whichcovers outlet port 36 at the top of first chamber 33. Preferably, inletport 30 is located at the bottom of first chamber 33.

Second chamber 41 of combined air barrier and liquid sequencing valvehousing 32 as shown in FIGS. 2-5 preferably has an inlet port at its topand an outlet port at its bottom. Second chamber 41 has means associatedwith its ports that are substantially impervious to air while the set isin use and prevent the flow of air through the secondary flow path. Asshown in FIG. 2, the outlet from second chamber 41 is covered by ahydrophilic membrane filter 45.

Hydrophilic membranes 38, 45 are impermeable to air when wet, which theyare during the use of the sets of this invention. The hydrophilicfilters can be formed from materials such as a cellulose acetatematerial produced by the Millipore Filter Corporation of Bedford, Mass.or the Sartorius-Membranfilter GmbH of Weender Landstr, West Germany.

The housing 32 of the set shown in FIG. 2 includes an air vent tube 47having a slide clamp 49 and a filtered opening 50. Alternatively,opening 50 can be filtered by a hydrophobic membrane filter which ispermeable by air, but not liquids. The hydrophobic filters can be formedof polyfluorotetraethylene, hexafluoropropylene/tetrafluoroethylenecopolymer, or other suitable materials. One such filter is made ofGelman ANH-450 material made by Gelman Instruments of Ann Arbor, Mich.When such a hydrophobic filter is used, slide clamp 49 can beeliminated, as shown in the set of FIG. 5, which includes both ahydrophobic filter over opening 50 and a hydrophilic membrane filter 51between opening 50 and second chamber 41. Alternatively, the air ventcan be eliminated altogether in those instances where the second chamber41 can be primed through its inlet port.

The sets of FIGS. 2 and 5 each include a slide clamp 51 near the distalend of secondary tube 19 and a slide clamp 52 near the proximal end ofcommon tube 21.

The combined air barrier and liquid sequencing valve shown in FIG. 2 hasan aperture in vertical wall 34 near its top which is covered by ahydrophobic membrane 53. Membrane 53 prevents liquid from passingbetween first and second chambers 33, 41 but permits air to pass. Secondchamber 41 has a reservoir 55 for liquid which has an open top locateddirectly under the opening to second chamber 41. Preferably, verticalwall 34 can be an integral part of reservoir 55.

For simplicity, the equipment sets embodying the system of FIG. 1 havebeen depicted and described as integral units in FIGS. 2 and 5. It isapparent, however, that the sets can be manufactured and assembled insubsets of the entire set and that each subset will accordingly beprovided such resealable closures, piercing means, adapters, etc. as arenecessary to permit their easy assemblage into the complete set at anappropriate time. It will also be apparent that some of the severalcomponents of the sets of FIGS. 2-5 can be interchanged or combined incombinations other than those specifically depicted.

OPERATION OF THE SYSTEM

As depicted in FIGS. 2-5, primary container 11 is suspended in space ata height above the patient by means of a hook 77 and stand 79. It willbe apparent that other means for suspending the containers of thisinvention are well known.

To insure that all the air that might be forced into the patient hasbeen removed from the set, the set is initially primed by first closingall slide clamps 49, 51, and 52, if present. Piercing pin 23 is theninserted into the resealable closure of primary container 11. Primaryflow control 31 is fully opened. Slide clamp 52 is opened to allowprimary liquid to flow through the primary liquid flow path and forceall the air therefrom that might be forced into the patient. Slide clamp52 is then closed.

In the sets of FIGS. 2 and 5, air will pass through hydrophilic membrane38 initially until the primary liquid fills first chamber 33 and thenwets hydrophilic membrane 38 as it passes through it. Then air will nolonger pass through membrane 38.

Secondary flow control 43 and clamp 49 on air vent 47 of second chamber41 are then opened to allow primary liquid to flow into, or back-prime,secondary flow path 19 until the liquid is above and forces all the airtherein above the outlet to second chamber 41, in the set of FIG. 2.Slide clamp 49 is then closed. When the set of FIG. 5 is employed,primary liquid will flow into, or back-prime, secondary flow path 19until liquid reaches and wets hydrophilic membrane 51, which can then nolonger vent air, thereby preventing the further flow of liquid intosecondary tube 19. In the sets of FIGS. 2 and 5, liquid will have nowwetted hydrophilic membrane 45 and air will not pass through it. Asubstantial volume of air will remain in second chamber 41.

Optionally, where the proximal end of secondary tube 19 is detachablefrom y-tube 29, it will be readily apparent that secondary flow control43 can be fully closed during the priming of primary tube 17 and remainclosed during the initial use of the set for the administration of aprimary medical liquid. Subsequently, when it is desired to administer asecondary liquid to a patient, piercing pin 35 at the distal end ofsecondary tube 19 can be inserted into the resealable closure ofsecondary container 13, the proximal end of secondary tube 19 detachedfrom y-tube 29, slide clamp 51 opened and secondary liquid allowed toflow through secondary tube 19 until it reaches the proximal endthereof. Slide clamp 51 is then closed and the proximal end of secondarytube 19 reattached to y-tube 29.

Common tube 21, which preferably has an adapter at its proximal end opento the flow of liquid therefrom, is next connected to needle 15, whichwill generally have been already inserted into a vein of the patient.Slide clamp 52 will then be opened to allow primary liquid to flowthrough the primary liquid flow path to the patient's vein. Primary flowcontrol 31 is then adjusted to a setting that will provide the desiredflow rate for a prolonged infusion of primary liquid into the patient,generally 10-150 ml./hr. As is well known in the medical practice, thatflow rate can be visually observed by viewing and counting drops passingthrough the primary drip chamber 25.

Alternatively, when it is desired to administer a secondary liquid to apatient using the sets of FIGS. 2 or 5, piercing pin 35 of secondarytube 19 is inserted into the resealable closure of secondary container13. If the portion of secondary tube 19 above the inlet port to secondchamber 41 is detachable, it can then be detached and slide clamp 51opened to force the air from that portion of tube 19. Slide clamp 51 isthen closed and the tubing attached to the inlet port to second chamber41.

Secondary container 13 is then suspended in space at a heightsubstantially greater than the height of primary container 11. The setwill now be in the mode illustrated in FIG. 2.

When slide clamp 51 is opened, secondary liquid will then immediatelybegin to flow into reservoir 55 of second chamber 41. Becausehydrophilic membrane 45 was wetted during the initial priming of the setand because slide clamp 49 is closed, or hydrophilic membrane 51 is wet,air can only escape from second chamber 41 through the aperture invertical wall 34 into first chamber 33. Thus, as secondary liquid entersreservoir 55, the air it displaces will be forced through hydrophobicmembrane 53 into first chamber 33 by the pressure of the secondaryliquid.

Because hydrophilic membrane 38 is wet, air in first chamber 33 cannotpass through it. Therefore, as the pressure of secondary liquid enteringreservoir 55 continues to force air through membrane 53 into firstchamber 33, that air will accumulate along the top wall of chamber 33.Because the pressure of secondary liquid forcing the air into chamber 33is greater than the pressure of primary liquid contacting the air, theair displaces the primary liquid in first chamber 33.

The displaced primary liquid is forced away from outlet 36 of firstchamber 33 through inlet 30 into primary container 11, as shown in FIG.3. Thus, hydrophilic membrane 38 and the air displaced from secondchamber 41 block the flow of primary liquid from primary container 11through the primary liquid flow path as long as the height of secondaryliquid in the system is greater than that of the primary liquid.

As shown in FIGS. 3 and 5, once reservoir 55 becomes filled withsecondary liquid, it will overflow reservoir 55 and flow out of secondchamber 41 through its outlet port. Secondary flow control 43 is thenadjusted to a desired flow rate, typically 50-250 ml./hr., for thesecondary liquid, which will then flow until the liquid in secondarycontainer 13 is depleted. It will be apparent that the initial liquidflowing from secondary tube 19 will be the liquid with which it wasprimed.

When the height of primary liquid in the system of FIG. 1, as depictedin the sets of FIGS. 2 and 5 becomes greater than the height of thesecondary liquid, the valve means associated with the ports of firstchamber 33 will immediately open and allow primary liquid to flow fromthe primary container at the flow rate to which primary flow control 31is adjusted. Because the pressure of the primary liquid pushing on theair at the top of first chamber 33 is now greater than that of thesecondary liquid, the primary liquid forces the air back into secondchamber 41, as shown in FIG. 4, thereby unlocking the "air lock" thathad prevented primary liquid from flowing out of first chamber 33.

The primary flow rate is independent of the secondary flow rate. Inthose instances where it is less than or equal to the secondary flowrate, both primary and secondary liquid will flow through common tube21, until air reaches the air barrier in second chamber 41. Then onlyprimary liquid will enter common tube 21. The air barrier in secondchamber 41 then prevents air from being drawn into common tube 21 andeventually to the patient's vein.

When primary container 11 becomes depleted of primary liquid, theprimary piercing pin 23 is merely removed therefrom and inserted intothe resealable closure of a new primary container, which is thensuspended in place of the previous container. When secondary container13 becomes depleted of secondary liquid, it can be left empty untilanother secondary liquid is to be administered. When another secondaryliquid is to be administered, the secondary piercing pin 35 is merelyremoved from secondary container 13 and inserted into a new secondaryliquid container. The combined air barrier and liquid sequencing valveis then briefly inverted to spill any liquid from reservoir 55 remainingtherein and the procedure used for initiating the flow of secondaryliquid from the first secondary container is repeated.

Having described the invention in specific detail and exemplified themanner in which it may be carried into practice, it will now be readilyapparent to those skilled in the art that innumerable variations,applications, modifications and extensions of the basic principlesinvolved may be made without deparating from its sphere or scope.

I claim:
 1. A combined air barrier and liquid sequencing valve providingseparate flow paths therethrough for a first and second liquid,preventing the passage of air from said separate flow paths andeffecting the automatic interruption of the flow of said first liquidwhenever said second liquid is flowing therethrough under a greaterpressure than that of said first liquid and the automatic resumption ofthe flow of said first liquid whenever the flow of said second liquidthrough said valve ceases, said valve comprising:a housing divided intofirst and second chambers by a vertical wall having an aperturetherethrough, said aperture covered by a hydrophobic membrane, wherebyair can pass between said first and second chamber, said first chamberhaving an inlet port thereto, and an outlet port at the top thereofcovered by a hydrophilic membrane, whereby air is prevented from passingthrough said outlet, said second chamber having an inlet port thereto,and an outlet port therefrom covered by a hydrophilic membrane, wherebyair is prevented from passing from said outlet, and a reservoir forliquid spaced between said inlet and outlet thereto, said reservoirhaving an open top located directly under said inlet port to said secondchamber, whereby, with said primary liquid flowing through said firstchamber, said secondary liquid entering said second chamber through saidinlet port thereto fills said reservoir until said secondary liquidoverflows from said reservoir and flows through said outlet port thereofand air present in said reservoir prior to its displacement therefrom bysaid secondary liquid escapes from said second chamber through saidhydrdophobic membrane covering said aperture in said vertical wallbetween said first and second chambers under the pressure of said secondliquid, thereby forcing said first liquid away from said outlet to saidfirst chamber and interrupting the flow of said first liquid until theflow of said second liquid through said second chamber ceases and allowssaid first liquid to force said air through said hydrophobic membraneand resume flowing through said first chamber.
 2. The combined airbarrier and liquid sequencing valve defined in claim 1, wherein saidinlet port to said first chamber is at the bottom thereof and said inletand outlet ports to said second chamber are respectively at the top andbottom thereof.
 3. The combined air barrier and liquid sequencing valvedefined in claim 1 or 2, wherein said reservoir is integral to saidvertical wall between said first and second chambers.
 4. The combinedair barrier and liquid sequencing valve defined in claim 1, 2 or 3,wherein said second chamber further includes a closable air ventthereto.
 5. The combined air barrier and liquid sequencing valve definedin claim 4, wherein said air vent is covered by a hydrophobic membrane.6. The combined air barrier and liquid sequencing valve of claim 5,wherein said air vent further includes a hydrophilic membrane betweensaid second chamber and said hydrophobic membrane.